Light and darkness symbolize humanity’s awareness and understanding, or a lack thereof, literalizing the idea of enlightenment in “Report on the Threatened City.” In the story, the alien envoys and their spacecraft are made of light and are thus difficult for the humans—with their limited understanding and still-developing technology—to perceive. The ship can be seen in dim moonlight, and the envoys’ first encounter with humans happens at night, suggesting the dimness of human awareness. And indeed, the youths and elders with whom the envoys communicate are aware of the imminent danger of an earthquake (which the envoys have come to Earth to warn people about) but cannot imagine taking preventive steps against it. The aliens themselves seem to be made of light rather than matter, which suggests that they are generally more enlightened—that is, technologically advanced, knowledgeable, and empathetic—than humans. The younger humans are more “clear-minded” than the elders, though, and thus better able to discern the dangers posed by war or the intersection of human action and nature. When the envoys encounter some intoxicated youths, the drug they have taken increases their sensitivity and enables them to better sense the envoys, whom they associate with light shining above the roof of a gas station.
When the envoys infiltrate a youthful gathering on the beach at sunset, they learn that darkness has a “powerfully saddening effect” on the humans, and the envoys’ messages inspire “disabling despair,” sad songs, and a hopeless refrain of “what can we do?” that lasts until many of the youth commit suicide. In this way, darkness represents people’s despair at not being able to understand the world around them. It is also at sunset—a time that, to the alien envoys, symbolizes humanity’s apathy and passivity—that the envoys abandon their failed mission of warning the city’s residents about the earthquake. The shifting and unstable light of sunset both indicates the challenges of enlightening the humans and provides the opportunity for the “official explanation” that shifting light and vivid sunsets cause mirages—illusions. Yet the envoys are real, and so is the danger of the earthquake. Nevertheless, humans perceive the envoys as a trick of the light and the earthquake as a vague, unurgent danger, thus perpetuating their own shortsightedness.